1. Field of the Invention
The present invention relates in general to computer buses and more particularly to a method and apparatus for handling power consumption of a bus-controlled component such that the power requirements of the bus-controlled component are met without drawing excessive power from the computer bus.
2. Related Art
Computer buses are an integral and vital part of a computer system that provide a path by which data travels within the computer system. Typically, the computer bus is a collection of wires that connects one part of the computer with another. For example, an internal bus connects internal computer components to a central processing unit (CPU) and main memory, while an expansion bus connects bus-controlled components (such as expansion boards or adapters) to the CPU and main memory. A computer bus includes a data bus, which transfers the data, and an address bus, which transfers information regarding where the data should go. The expansion bus includes a bus connection (such as a bus slot) into which the bus-controlled component is inserted to add capability to the computer. In general, the bus-controlled component is a printed circuit board such as, for example, a video adapter, graphics accelerator, sound card, accelerator board and an internal modem.
One popular type of computer bus is the local bus architecture. Local bus architecture includes both the Industry Standard Architecture (ISA) expansion bus and the Peripheral Component Interconnect (PCI) local bus. In general, the PCI local bus is a newer architecture than the ISA architecture and provides fast throughput that allows data to be exchanged rapidly by connecting directly or nearly directly to the CPU. In addition, the Accelerated Graphics Port (AGP) architecture is closely related to the PCI architecture and used for video bus-controlled components. Each type of local bus architecture is governed by a set of rules or standards that specify operational parameters. These standards include a rule dictating the maximum amount of power that a bus-controlled component should draw from a bus connection or slot. For example, the PCI standards call for a maximum of 25 watts of power to be drawn from a PCI bus slot in a computer. The reason for these power standards is that the additional draw of power through any individual bus connection or slot may cause unwanted induction or other artifacts that will degrade the signals of the bus-controlled component and substantially decrease the reliability of the entire computer bus.
One problem, however, is that bus-controlled components, such as those using the PCI or AGP bus standard, are becoming increasingly complex and are often expected to drive other power-consuming devices. In order to drive these other devices, bus-controlled components typically must draw 100 watts or more of power from the bus connection (or slot) into which they are inserted. There are currently two techniques used to deal with the additional power requirements. First, the bus-controlled component is designed to draw power from more that one bus slot even though it is inserted into a single bus slot. Depending on the power required, the bus-component could be drawing power from its own bus slot as well as several adjacent bus slots. This technique effectively disables adjacent bus slots and can severely limit the number of bus-components that may be used in a computer. In addition, the reliability and longevity of the bus-controlled components are degraded.
Another technique used to deal with additional power requirements is to simply ignore the computer bus standards and draw all the required power from a single bus slot into which the bus-controlled component is inserted. The problem with this technique, however, is that the reliability and performance of the entire computer bus is adversely affected. Moreover, this technique merely avoids the problem by allowing the problem to reintroduce itself as power demands for future bus-controlled components increase. The use of either technique involves the risk of damaging the computer bus or other computer system components that are not designed to handle the increased power load.
Accordingly, what is needed is a method and apparatus for enhanced handling of the additional power consumption requirements of a bus-controlled component that does not use either of the above-mentioned techniques and solves the power consumption problem. In particular, what is needed is a method and apparatus for power consumption handling of a bus-controlled component that does not draw power from adjacent bus slots. Moreover, what is needed is a method and apparatus that adhere to the standards for the computer bus and do not draw a greater amount of power from the bus slot than allowed by the bus standard, thereby increasing the reliability and longevity of the computer bus and components.